title: Murine protein serine/threonine kinase 38 activates apoptosis signal-regulating kinase 1 via Thr 838 phosphorylation.
abstract: Murine protein serine/threonine kinase 38 (MPK38) is a member of the AMP-activated protein kinase-related serine/threonine kinase family that plays an important role in various cellular processes, including cell cycle, signaling pathways, and self-renewal of stem cells. Here we demonstrate a functional association between MPK38 and apoptosis signal-regulating kinase 1 (ASK1). The physical association between MPK38 and ASK1 was mediated through their carboxyl-terminal regulatory domains and was increased by H(2)O(2) or tumor necrosis factor alpha treatment. The use of kinase-dead MPK38 and ASK1 mutants revealed that MPK38-ASK1 complex formation was dependent on the activities of both kinases. Ectopic expression of wild-type MPK38, but not kinase-dead MPK38, stimulated ASK1 activity by Thr(838) phosphorylation and enhanced ASK1-mediated signaling to both JNK and p38 kinases. However, the phosphorylation of MKK6 and p38 by MPK38 was not detectable. In addition, MPK38-mediated ASK1 activation was induced through the increased interaction between ASK1 and its substrate MKK3. MPK38 also stimulated H(2)O(2)-mediated apoptosis by enhancing the ASK1 activity through Thr(838) phosphorylation. These results suggest that MPK38 physically interacts with ASK1 in vivo and acts as a positive upstream regulator of ASK1.
authors.affiliation: Department of Biochemistry, Biotechnology Research Institute, School of Life Sciences, Chungbuk National University, Cheongju 361-763, Republic of Korea.
authors.forename: Haiyoung
authors.initials: H
authors.lastname: Jung
authors.forename: Hyun-A
authors.initials: HA
authors.lastname: Seong
authors.forename: Hyunjung
authors.initials: H
authors.lastname: Ha
mesh_terms: D000818:Animals; D017209:Apoptosis; D002460:Cell Line; D004789:Enzyme Activation; D006801:Humans; D006861:Hydrogen Peroxide / Q000494:pharmacology; D048670:MAP Kinase Kinase 4 / Q000378:metabolism; D048848:MAP Kinase Kinase Kinase 5 / Q000378:metabolism*; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D013912:Threonine / Q000737:chemistry; D015533:Transcriptional Activation
chemical_list: D013912:Threonine; D006861:Hydrogen Peroxide; C108524:Melk protein, mouse; D017346:Protein Serine-Threonine Kinases; D048848:MAP Kinase Kinase Kinase 5; C482859:Map3k5 protein, mouse; D048670:MAP Kinase Kinase 4